<!DOCTYPE html>
<html lang="cn">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
        header{
            height: 100px;
            width: 100%;
            background-color: #369;
            display: block;
        }
        nav{
            height: 50px;
            width: 100%;
            background-color: #ccc;
        }

        div{
            height: 450px;
            width: 100%;
            background-color: #f90;
        }

        footer{
            height: 50px;
            width: 100%;
            background-color: #09f;
        }
    </style>
    <script>
        // document.createElement('header');

    </script>
    <script src="./html5shiv.min.js"></script>
</head>
<body>
    <header>
        <nav></nav>
    </header>
    <div></div>
    <footer></footer>

</body>
</html>